Rules of thumb for guttering and number of downpipes?

Hi,
Warmer weather cometh and it's time to put the guttering back...
I have 4 downpipes.
One is blocked, but only served a 3m bit of flat roof and there's a gulley
drain nearby (yes I already pay for rainwater down the drains).
Of the other 3, 2 are at the front of the house and one at one end of the
rear - 3 corners basically.
I *thought* these were connected to the sewer, but a test with a hose shows
they are not - and more annoyingly, that one is blocked and holed and
spewing water below ground (below concrete).
I'm considering switching to just the two diagonally opposed downpipes. Gawd
knows where they go, but they seem to run free.
For a hipped roof 11.6 x 8m (bungalow) are two downpipes diagonally opposite
likely to cut the mustard? The guttering is 4.5" half round - though a lot
had rusted away, and whilst I could use a deep section to replace it, I'd
waste a fair amount of good guttering.
It would be unwelcome work at this stage to investigate the blocked drain -
though I am tempted to buy a 40 quid 5m-leaded usb camera from ebay to make
sure the other 2 drains go a reasonable distance from the foundations.
BTW - what is a resonable distance? I seem to recall 5m being mentioned
somewhere as current standards, but should I worry if it was 2m, or 3m?
Cheers!
Tim

Snippage.
ISTR rainwater provision is based on 3/4" in one hour. Somebody else may
know more.
Blocked soaks here are invariably caused by roof and gutter debris
collecting at the outlet to the soakaway pit and eventually blocking the
pipe. As you say, 5m is the current minimum distance from foundations
but BCO may have agreed something different. If you have two drains fed
to the same soak and can determine the direction of the pipes then a bit
of drawing may fix the place to dig. Rainwater gulleys rarely have
rodding access which would otherwise give you a direction and distance .

Tree roots, particularly Leylandi can be a problem but more common on
damaged sewers.

Over to Hugo. I would be very worried if the soil was sandy at 2-3m
distance.

Hi,
Probably not in 1950 :) Or 1970... These soakways are either original or
modified when some mods were done to the house.

The one that is blocked seems to be full of debris - I managed to shove a
hose down and clear the first blockage, which is when it spewed forth from
just below ground - probably a holed pipe (thin steel) combined with
blockage.

We're solid clay here - the foundation strip sits on the clay.
It might be prudent to lay some new soakaways in.
One of the apaprantly working soaks goes under the drive, so I'm hoping to
not have to touch that. Good candidiate for a camera.
The other two are not too bad - 3ft concrete path in the way, but I want to
get rid of that, so chopping a bit out will do no harm.
As we have very heavy clay not far down, I'm wondering if a land drain pipe
on the end of a plain pipe (to distance itself from the building) and bury
the landdrain in gravel might be the way to go, Dump the water over a 3m
length of garden perhaps.
I would put traps in at the downpipe base this time, with clearing access -
to catch grit if nothing else.

Tim, our bungalow is about the same roof size, and like yours originally had
a downpipe at each corner. We built an extension on the end, and as part of
the roof extension rejigged the gutters. At the front I was persuaded by our
(otherwise very good) builder to go for one central(ish) down pipe. It was
fine in gentle rain, but in a decent downpour didn't cope, and we had water
pouring over the gutter rims - even with the outlet fully clear. I've now
gone back to a downpipe at each end, and the problem has gone away, even
with some leaves and moss in the outlets..
Charles F

Thanks Charles,
That's useful to know.
I'm now going to try to toss up whether to fix the blocked drain or to use a
deep profile gutter.
I really wanted to keep the cast ali gutters. That is available in deep
profile, but it's *very* expensive (whereas the half round cast ali gutters
are just *expensive*).
I have the BCO coming round anyway to sign off the roof retile, so I will
seek guidance re proper soakways.
I guess I could put the gutter back with the current downpipe patten and
divert the blocked downpipe to run over the concrete path in the meantime -
that has a string slope downhill away from the house and will disperse the
flow over a wide strip of earth 1.5m away from the house.
Will be better than injecting it right by the foundations, at least for a
couple of months...
*sigh* the work never ends...
Cheers,
Tim

Recognising your wish to retain the look of metal guttering, I still think
in the long term you may be better off changing to deep profile plastic
guttering.
The number of issues you describe with the blocking of the soakaways, the
leaking pipes, the clay subsoil, tracing underground pipes etc. suggest
that you may be storing up similar problems in the future.
We have nearly all our roof (3 bed semi and car port and veranda) going
into a single downpipe into the sewers and so far it seems to cope.
In the long run it is probably best to just bite the bullet and replace
all the guttering.
Places like fascias.com can supply at a reasonable cost.
Cheers
Dave R

You can get deep profile "cast effect" -
http://www.drainageonline.co.uk/
The only thing that annoys me about plastic is leaning ladders against it...
Sadly, re sewers, I have one pit that would be easy to make a connection and
is 2m from a downpipe - but it's the "wrong" corner - at the back. Are you
allowed to make new sewer connections for rainwater?
So I'm going to have to go with soakaways... As I say, redigging 2 is not
too bad given it'll be an 18" deep trench (no point in going lower as it's
all clay).
The only one I will have to hope is OK is the one under the drive - that
would be a right PITA to dig up, though I could still camera it.

In theory if you make any changes to the soil pipes you need Building
Control approval.
However it is quite unlikely that anyone would notice, so you have to
decide if you want to be pragmatic.
Our builders were amazed that I took photos of the new drain run to the
shed at the bottom of the garden to show to BC - they told me I was
telling BC far too much :)
We did it quickly because we had a digger on hire and there was an
opportunity to dig, lay, and backfill all in one day.
With regard to the 'wrong corner', I assume that if you renew all the
guttering then you can organise the flow whichever way you want.
Our guttering has always flowed from the front of the house to the far
corner of the back (don't know why but they all do it), so the longest
possible run instead of meeting at a half way point.
I don't know your layout, but I can't help thinking that replacing all the
guttering with new, all sloped to one downpipe which goes into a
convenient manhole, might be easier that re-engineering several downpipes
and variable slopes.
Still, you are the one doing it :)
Best of luck.
Dave R

Yes, indeed :)
It might be sane to send the west side round there where there'll be a
centre downpipe which I can drop into a handy gully drain (to the sewer) for
now (if not forever).
The south side with the bays will easily run down the east side (straight)
run) to the unblocked corner drain - and if I find out that is too near the
house, it is also the easiliest to redig.
This shows what I mean (needs fixed font)
ROAD ROAD ROAD ROAD ROAD ROAD ROAD ROAD ROAD ROAD
LOW GROUND
South
East West
Main
Sewer DRIVE DRIVE DRIVE
^
|
| <<<< <<<< >>>>
| ========= ========= ========= V
| V | | | | | |
| == ========== ==== === V
| V | |
| | |
| | |
| | | V HIGH GROUND
| V | |
| | |
| | |
| D1| |
| =============================== | V
S1---- >>>> G D2<<<| |
| \ ---- | ============ | \ / <<<<
| ------------S2--------------S3
North
It's a bit weird but it could work and give me 2 sewer connections.
Key: >>> <<<< V show rain flow direction in gutter
S1,S2,S3 are sewer manholes and the lines between show the sewer runs.
G is an existing gulley drain ton the sewer
D1, D2 proposed downpipes.
D1 esists now into a soakway in unknown location.
There is a blocked soakway downpipe on the SE corner.
There is another working, but unknown location soakaway connection
on the SW corner - probably under the drive.
D2 is no problem - into gulley.
D1 could be hooked into inspection chamber S1 easily (it's new and has a
spare inlet blanked off in the right side).
My gut instinct is that a deep gutter would probably manage to route that
flow.
What's the panel think?
HIGH GROUND

Well, if the above works, one will be going into a gully to sewer and the
other could be connected to a manhole 1.5m away.

Yes - I'm tempted.
Who's better: Brett Martin[1] or Floplast?
http://www.drainageonline.co.uk/Guttering/Brett-Martin-Guttering.htm
http://www.fascias.co.uk/contents/en-uk/d537_Guttering_Systems.html
There's both a round deep style and a stepped-square style - either would
probably look good and the latter has massive flow rates.
[1] I've had a bit of Brett Martin's half round cast effect - not bad from a
distance, but a bit of a bitch to clip.

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